How to solder a conductor to the surface contact of a high-power LED matrix?

Question

Soldering

4 questions:

question 1
hot air gun mode to solder the conductor to the pins of the 20W COB matrix (+ and -):



question 2
Which side to blow with a hot air gun - from below (from the back, where the radiator will be) or from above (where the contacts and silicone themselves) ? If you blow from below, the entire sheet of metal, the entire matrix, will probably warm up ... And if you blow from above, on the contacts, with a narrow stream of 200 °, how not to burn the optical silicone? Cover it with foil? How long does it all take?

question 3
What kind of flux is used in such cases?
There is LTI-120 and "acid" FCA.

question 4
And what are the recommendations for soldering if the product will then be used at -20°C?

PS Soldering station Lukey 702

Answer 1

With an ordinary soldering iron of 60 watts at the maximum temperature, it is soldered without any problems, you just need to hold it a little longer.

Answer 2

From below - heating up to 100-120 degrees on a tile or iron (if there is no special heated table). Yes, you put the entire matrix directly on the iron, nothing will deteriorate there. You can blow a hair dryer from below, but it's not so convenient.
From above - solder with an ordinary soldering iron. Flux - not active (without acid), LTI is quite suitable. Solder - ordinary tin-lead, for example POS-60.